title: The cascade radical cyclisation approach to prenylated alkaloids: synthesis of stephacidin A and notoamide B.
abstract: A strategy for the synthesis of members of the prenylated indole alkaloid family is described, which involves a radical cascade process of an appropriately substituted diketopiperazine (DKP) core structure. Several approaches to the generation of the initial radical were explored, with the most successful involving treatment of a sulfenyl substituted DKP under classical reductive conditions by heating with Bu3SnH and a radical initiator. The required, fully substituted, radical precursor DKP structures were prepared using regio- and stereocontrolled enolate chemistry of simpler proline-tryptophan derived DKPs. The new approach allowed rapid access to a key polycyclic indoline structure, which was converted into either of the natural products stephacidin A or notoamide B.
authors.affiliation: School of Chemistry, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK. n.simpkins@bham.ac.uk
authors.forename: Nigel S
authors.initials: NS
authors.lastname: Simpkins
authors.forename: Ilias
authors.initials: I
authors.lastname: Pavlakos
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weller
authors.forename: Louise
authors.initials: L
authors.lastname: Male
mesh_terms: D001688:Biological Products / Q000138:chemical synthesis / Q000737:chemistry; D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D026121:Indole Alkaloids / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D001688:Biological Products; D005609:Free Radicals; D026121:Indole Alkaloids; C520596:notoamide B; C470895:stephacidin A